crazyness - My Cat has changed

my cat used to be nice however recently his balls turned yellow and he became very mean when they did how can i fix this the vet has no idea what it is

Answer from KAteHiWell I dont know what to say to this. if the vet does not know what the issue is then I have no way of knowing either.

i assume from your text that your cat is not neutered. i wonder if his crazy behavior as you say could be caused by hormones. Speak to your vet to see if this could be a possibility and also whether or not he recommends neutering to tray and calm the situation